Probit Model

Also known as · probit · probit regression

The probit model is a binary-outcome model that estimates Pr⁡(y=1∣x)=Φ(x′β)\Pr(y = 1 \mid \mathbf{x}) = \Phi(\mathbf{x}'\boldsymbol\beta), where Φ\Phi is the standard-normal CDF. By squashing the linear prediction x′β∈(−∞,+∞)\mathbf{x}'\boldsymbol\beta \in (-\infty, +\infty) into [0,1][0, 1], probit cures the LPM's out-of-range-probability problem; the price is non-linearity in parameters, so the model is estimated by MLE rather than OLS.

When to use

Use probit when the LPM's unbounded predictions or constant marginal effects are uncomfortable — typically when many fitted values approach 0 or 1, or when the substantive question is about probabilities at the extremes. In practice probit and logit give nearly identical predictions; the choice rarely matters. Raw coefficients β^j\hat\beta_j tell you the direction only; for the probability change you need the marginal effect φ(xˉ′β^)⋅β^j\varphi(\bar{\mathbf{x}}'\hat{\boldsymbol\beta}) \cdot \hat\beta_j (see the Computing marginal effects (logit / probit) recipe). Hypothesis testing uses the Likelihood Ratio Test rather than the F-test.

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